In Phase I of the program, LEEOAT Company will develop, design, simulate and optimize the architecture of the two-dimensional circular apertured ultrasonic phase-array transducer (2DUPAT) for high-resolution, real-time medical imaging applications. This high-density 2D matrix transducer will be based on LEEOATCompany's novel micromachining technology. Additionally, based on our expertise in high-density electronic interconnections, LEEOATCompany will couple the 2D-UPAT with the designed transmit/receive electronics to result a small-size, highperformance volumetric medical imager. We will theoretically model and simulate the 2D-UPAT and the corresponding electronics and predict the performance of the device for real-time, high-resolution medical volumetric imaging. We will demonstrate the proof-of-concept by micromachining a sample of the phase-array transducer and conduct pulse/echo experiments. Finally, we will estimate the cost/effort for the fabrication and testing of a 2D-UPAT imaging system prototype for medical applications, to be performed in Phase II of the SBIR program.